Quasi Drain Valve

I have a zone that is all above-ground PGPs. Accordingly, I need to drain it to stop winter frost damage. The lowest part of the zone is a Hunter valve, in a box. The valve is isolated from the mains by a ball valve. (It's an Irritrol controlled solenoid valve)

My question is - rather than install a special drain point - can I close the isolating valve and remove the solenoid and thereby drain the zone? I.e. Will water lying in the sprinklers and pipes drain slowly back through the now-open valve's solenoid orifice?